1. Field of the Invention
The present invention relates to a recording or reproducing apparatus of the rotary head type which can magnetically record a digital signal, and more particularly to a digital VCR (Video Cassette Recorder) which can record and reproduce plural signals of different data rates and surely reproduce data even when data are searched at a high speed.
2. Description of the Related Art
Conventionally, as a method of recording and reproducing plural signals of different data rates in a VCR, known is a method which is described in a publication of IEEE Transactions on Consumer Electronics, Vol. 40, No. 3, P. 263-268. This publication shows a technique of conducting multirate recording in a digital VCR without changing a recording density.
In the method, two heads of different azimuth angles are mounted on a rotary drum so as to be opposed to each other at a central angle of 180xc2x0. These heads are called a first head and a second head, respectively. When the rotary drum rotates, the first and second heads alternately scan a tape. Hereinafter, the description is made only on the recording operation. The reproducing operation is conducted in the same manner.
In normal record and reproduction (1-speed record and reproduction) in which an image is recorded and reproduced at a normal speed, a magnetic tape (hereinafter, referred to as merely xe2x80x9ctapexe2x80x9d) is caused to run at a predetermined speed (1-speed). First, the first head scans the tape, and the second tape then scans the tape so that signals are sequentially recorded.
In the ⅓-speed record and reproduction mode (⅓-speed record and reproduction) in which the rate of data to be recorded is one third that of the normal record and reproduction, the tape speed is reduced to ⅓. First, the first head scans the tape and records a signal. Next, the second head scans the tape and the first head then conducts the second scan. In the scan of the second head and the second scan of the first head, a signal is not recorded. When the second head then scans the tape, a signal is recorded. Similarly, when the first and second heads then scan the tape in sequence, a signal is not recorded. In the next scan of the first head, a signal is recorded. Then, the operation state returns to the initial state. The recording at the ⅓-data rate is conducted by repeating the above operation. In a similar manner, a signal can be recorded and reproduced at a 1/n-data rate (where n is a positive odd number).
In addition to the configuration, a third head of an azimuth angle which is different from that of the first head may be colocated or placed at the same position so that, even when n is an even number, record and reproduction are enabled. Since the first and third heads are colocated, the scan operations conducted by the two heads are substantially coincident with each other.
When a signal of the data rate which is one half that of the normal record and reproduction is to be recorded and reproduced, for example, record and reproduction are conducted in the following manner. First, the tape speed is reduced to one half that of normal speed reproduction. When the first and third heads scan the tape, the first head conducts the signal recording but the third head does not conduct it. When the first and third heads scan the tape at the next time, the third head conducts signal record but the first head does not conduct it. Signal record at the xc2xd-fold data rate is conducted by repeating the operation.
Even when n is a positive even number, signals can be generally recorded and reproduced at a 1/n-fold data rate in a similar manner.
In such a prior art recording and reproducing apparatus, the first and third heads are to be colocated. Actually, however, it is difficult to dispose two heads at the same position, and hence the two heads are located at positions which are close to each other, respectively.
However, a prior art magnetic recording and reproducing apparatus is not provided with a measure against a problem which may be produced by the close arrangement of two heads. As a result, there arise problems in that the track width varies because the tape speed is changed in record modes of different data rates, and that the tracking margin which is tolerance for deviation of a head is reduced in search speed reproduction in which reproduction is conducted at a speed different from the normal one.
Conventionally, as a method of conducting search speed reproduction in a digital VCR, known is a method disclosed in Japanese Patent Publication (Kokai) No. HEI 2-94071.
In the disclosed method, when a video signal is to be recorded, a subcode area is formed on a tape. The subcode area is formed on the scanning locus of a head which is to be produced in search speed reproduction, and still image information extracted from the video signal is recorded in the subcode area in a distributed manner. In search speed reproduction, data recorded in the subcode area are reproduced so as to reproduce the still image information, thereby improving the image quality of variable speed reproduction.
In such a configuration, however, a speed at which still image information can be stably reproduced in search speed reproduction is restricted only to one kind. In a VCR at present, a speed of one kind is not sufficient for search speed reproduction. According to the prior art method, in order to cope with plural variable reproduction speeds, data must be recorded in a duplicate manner on all the scanning loci of heads which are to be produced in the plural variable reproduction speeds. This produces problems in that duplication of data is required so that reproduction of data is complicated, and that data are wasted.
In the prior art method, the record track must be made positionally coincident with the heads. Furthermore, the track in which the subcode area is formed must be selected in search speed reproduction, thereby producing a problem in that the mode shift from normal speed reproduction in which an image is reproduced at the normal speed to search speed reproduction requires a prolonged time period. In the prior art method, there is a further problem in that an AUX area in which additional information such as a program is to be recorded is disposed in the normal data area and hence information of the AUX area cannot be reproduced in search speed reproduction.
It is an object of the present invention to suppress the variation in track width when plural signals of different data rates are recorded.
It is another object of the invention to reduce the failure in obtaining search information and surely reproduce search data in search speed reproduction.
The present invention is to easily realize search speed reproduction of a high image quality in a simple data arrangement.
The present invention is to reduce wasted search data and realize search speed reproduction of plural speeds.
The present invention is to provide a recording and reproducing apparatus which can surely reproduce search data even when the phase indicative of positional deviation between a head and a record track is not controlled in search speed reproduction.
The present invention is to provide a recording and reproducing apparatus in which it is not required to select a track to be scanned in search speed reproduction and the mode can be smoothly shifted from normal speed reproduction to search speed reproduction.
The present invention is to provide a recording and reproducing apparatus in which even a head of a width substantially equal to a track pitch can reproduce all effective search data.
The present invention is to provide a recording and reproducing apparatus which can reproduce information of an AUX area also in search speed reproduction.
In order to attain the objects, the recording and reproducing apparatus of the invention comprises: tape driving means for driving a tape; a rotary drum around which the tape is to be slantly wound; three heads, first, second, and third heads which are mounted on the rotary drum and which scan the tape so as to conduct recording or reproducing operation; and a head control unit which controls the operations of the three heads. The azimuth angles of the three heads are set so that the first head has a first azimuth angle and the second and third heads have a second azimuth angle which is different from the first azimuth angle. The three heads have mutual positional relationships in which the first and second heads are mounted on the rotary drum so as to be opposed each other at a central angle of 180xc2x0 and at the same height in the rotation shaft direction of the rotary drum, and the third head is located in close proximity to the first head in the circumferential direction of the rotary drum with a minute difference in central angle and a minute height difference in the rotation shaft direction of the rotary drum.
According to this configuration, the minute height difference is set between the first and third heads which are disposed in close proximity to each other. When plural signals of different data rates are to be recorded or reproduced, therefore, the head scan error can be reduced and the variation in record track width can be minimized.
In order to attain the objects, the apparatus of the invention comprises a rotary drum around which a tape is to be slantly wound, and three heads, first, second, and third heads which are mounted on the rotary drum and scan the tape so as to conduct recording or reproducing operation. The azimuth angles of the three heads are set so that the first head has a first azimuth angle and the second and third heads have a second azimuth angle which is different from the first azimuth angle. The three heads have mutual positional relationships in which the second and third heads are mounted on the rotary drum so as to be opposed each other at a central angle of 180 deg. and the first head is located in close proximity to the third head in the circumferential direction of the rotary drum with a minute difference in central angle.
According to this configuration, since the second and third heads having the same azimuth angle (the second azimuth angle) are located at positions which are opposed to each other at a central angle of 180xc2x0, the deviation amount in scan position of the heads in search can be reduced and made always constant irrespective of the search speed. Even in a high speed search, therefore, search data can be surely reproduced.
In order to attain the objects, a plurality of heads having at least one azimuth angle are disposed. A normal data area used in normal speed reproduction which is reproduction conducted at the normal speed, and one or more search data areas used in search speed reproduction are disposed in one track. The reference speed for search speed reproduction which is a speed serving as the reference for search speed reproduction is set to be N1 [N1-speed] (where N1 is an odd number). The search data areas of a track set consisting of N1 or more tracks which are alternately selected are disposed at positions of the respective tracks and on the same line parallel to the tape running direction. The same data are recorded in the search data areas of the track set.
According to this configuration, each of the plurality of heads scans one time the track set, and hence it is not required to select the track to be selected. Even when the positional relationships between the heads and record tracks are not controlled, moreover, data can be complementarily reproduced by plural scans or all effective data of the search data areas can be reproduced by either of plural scans. Therefore, search speed reproduction of a high image quality can be realized in a simple data arrangement.
In order to attain the objects, a normal data area which is used in normal speed reproduction, and one or more search data areas which are used in search speed reproduction are disposed in one track. The reference speed for search speed reproduction is set. The search data areas of a track set consisting of a plurality of tracks are disposed at positions on the same line parallel to the tape running direction on the respective tracks. The search data areas of the track set have the same data. In reproduction at the reference speed for search speed reproduction, the positional relationships between tracks and the heads are controlled, and data of the search data areas of the track set are reproduced by two scans of the heads.
According to this configuration, the heads scan the search data areas two times in complementary positional relationships and hence all effective data of the search data areas can be complementarily reproduced. Therefore, it is not required to select a track to be scanned so that even heads which have the width substantially equal to the track pitch or a small tracking margin can realize search speed reproduction of a high image quality.
In order to attain the objects, when reproduction is to be conducted at a reproduction speed which is about two times the reference speed for search speed reproduction, a search data area is formed on a locus along which a head scans a tape, and, when reproduction is to be conducted at the reference speed for search speed reproduction, data of the search data area are reproduced by two scans of the head.
According to this configuration, even when a track to be scanned is not selected, reproduction can be conducted at the reference speed for search speed reproduction and a speed which is about two times the reference speed. Furthermore, all search data can be reproduced by heads which have the width substantially equal to the track pitch. As a result, the same data are commonly used in reproductions of different speeds, and hence it is possible to realize search speed reproductions of different speeds in which search data are not duplicately used.
In order to attain the objects, a normal data area which is used in normal speed reproduction, and one or more search data areas which are used in search speed reproduction are disposed in one track. The search data areas of a track set consisting of a plurality of tracks which are alternately selected are disposed at positions on the same line of the respective tracks. The same data are recorded in the search data areas of the track set. Data of the search data areas are reproduced by W scans (where W is an integer which is 3 or more).
According to this configuration, even when heads which have the width substantially equal to the track pitch are used in search speed reproduction, all effective data of the search data areas can be reproduced by W scans without requiring the control of the positional relationships between the heads and record tracks. Consequently, search speed reproduction of plural speeds in which wasted search data are reduced can be realized.
In order to attain the objects, a normal data area which is used in normal speed reproduction, and one or more search data areas which are used in search speed reproduction are disposed in one track. The search data areas of a track set consisting of a plurality of tracks which are alternately selected are disposed at positions on the same line parallel to the tape running direction on the respective tracks. The same data are recorded in the search data areas of the track set. The delimitation of the track set is indicated by the control signal.
According to this configuration, the detection of a track set can be simplified and it is not required to record data indicative of the delimitation of a track set, whereby search speed reproduction of a high image quality can be easily realized.
In order to attain the objects, a normal data area which is used in normal speed reproduction, and one or more search data areas which are used in search speed reproduction are disposed in one track. An AUX area is formed in a part of the search data areas.
According to this configuration, data recorded in the AUX area can be reproduced in both normal speed reproduction and search speed reproduction.